1
general::
Phrase(s): talk down to someone
to speak to someone in a patronizing manner; to speak to someone in the simplest way. • The manager insulted everyone in the office by talking down to them. • Please don’t talk down to me. I can understand anything you have to say.
McGrawhill's American Idioms And Phrasal Verbs
2
general::
Also, speak down to. Address someone with insulting condescension, patronize, as in Just because she's editor-in-chief doesn't give her the right to talk down to her staff, or Children hate teachers who speak down to them.
American Heritage Idioms